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Deciduous trees’ green leaves are turning to vivid yellows, luminous oranges and gleaming reds — signaling a change of season in the high Rockies.

Autumn officially begins on Sunday, marked by the fall equinox. On the two equinoxes every year the sun shines directly on the equator, and the length of day and night is nearly equal.

It’s right around this time that Colorado’s deciduous trees change color.

With less light on short days, trees and shrubs return to an energy-saving mode to survive the winter, according to Planttalk Colorado, a Colorado State University Extension website. Short days and falling temperatures signal trees and shrubs to quit producing chlorophyll, which converts sunlight into sugars through a process called photosynthesis.

On average, the best time to view color is in late September and early October. But late-season moisture has caused color changes to occur a little later than normal this year, according to Colorado State Forest Service forester Ryan McNertney.

“We are just starting to see pockets (of color) here and there, but it may start to pick up, especially if we start to see cooler temperatures,” he said.

The best places to view colorful native trees are in the lower elevations of Summit County, McNertney said.

The best places to view fall colors are in the lower elevations of Summit County